Cellulose ether film and composition for making the same



Patented June 11, 1929.

UNITED mm I F Fl STEWART J. CARROLL, OF ROCHESTER, NEW YORK, ASSIGNOR TO EASTMAN KODAK COMPANY, OF ROCHESTER, NEW YORK, A CORPORATION OF NEW YORK.

CELLULOSE ETHER FILM AND COMPOSITION FOR MAKING- THE SAME.

'No Drawing.

This invention relates to compositions of matter in which "cellulose ethers, such as water-insoluble ethyl cellulose, are combined or mixed with other substances which impart not only low infiammability, but likewise give coin 'iositions the other properties of which are also highly advantageous in the plastic and analogous arts, such, for instance, as the film or varnish arts.

One object .of the invention is to provide cellulose ether films having not only all of the ordinary desirable qualities of films for photographic purposes, but also having unusually low infiammability and extremely high resistance to deterioration by heat. Another object of the invention is to provide permanently transparent, strong, fiexible sheets or films of desired thinness, which are substantially waterproof, are unaffected by ordinary photographic fluids, are substantially colorless, are substantially without harmful action upon light-sensitive photographic coatings, are of low infiammability and highly resistant to prolonged heating. Another object of the invention is to provide compositions capable of easy manipulation in film making, varnish making, or allied plastic arts. Another object is to provide compositions which will not injure or be injured by the substances or surfaces with which they are associated during manufacture, storage or use. Other objects will hereinafter appear.

In U. S. Patent No. 1,188,376, Lilienfield, June 20th, 1916, there are disclosed a series of alkyl others of cellulose. Certain of these are particularly insoluble in water, and the present invention finds its chief valuein connection with ethers having this property, such as water-insoluble ethyl cellulose, films of which have small shrinkage characteristics, after treatment in photographic baths. In U. S. Patent No. 1,583,709, W'ebb, May 4th, 1926, there are disclosed films of such cellulose others in which the ordinary desirable qualities of photographic film base are combined with resistance to prolonged heating, this result being brought about by maintaining an alkalinit in excess of Ph,. It is desirable that such lms, especially motion picture films, be capable of withstanding heating without becoming brittle. Whether or not films will posses this proper- Applieation filed August 9, 1926. Serial No. 128,336.

ty can beforetold with practical accuracy by testing samples, say by heating them for weeks and even months at a continuous temperature of 65 C. Films which remain usefully flexible after such a severe test are capable of withstanding the conditions ihet with in use.

I have found that these qualities of the films may be maintained and yet the inflammability greatly lowered by incorporating bromcamphor in such films and in the compositions out of which they are made. When mixed into the film-making compositions, the bromcamphor should be free from free bromine and free hydrobromic acid. Otherwise they will cause sufficient discoloration to make the film undesirable for photographic purposes, will cause deterioration of any photographic emulsions placed upon the film, and will destroy the alkalinity upon which the resistance of the film to prolonged heating depends.

But I have found, as stated above, that if the brominated camphor is initially purified from free bromine and free hydrobromic acid and is incorporated in films having an alkalinity greater than Ph there is no acidity in the film-making solution, nor in the film, nor does this condition develop during the normal storage of the solution or during cam'phor in 300 to 500 parts of a volatile.

common solvent. The latter may usefully comprise a mixture of methyl acetate and methyl alcohol, the weight of the methyl acetate being approximately nine times the weight of the methyl alcohol. Of course, the ingredients of the solvent are of sufiicient purity to avoid acidifying the composition. This composition is suitable, for spreading upon a film-forming surface in a coating, from which the volatile solvent evaporates sufiiciently to leave a transparsuch bodies are not essential.

out, flexible sheet, which is stripped off and otherwise treated in a manner well known to those skilled in this art.

The ingredients in the film-forming comof only slight volatility whichdenhance the flexibility of the compositions and regulate the preparation of film therefrom; but Examples of them are amyl or butyl acetate, the various amyl alcohols, the various butyl alcohols, and mixtures of them. Of course, these ingredients are also sufficiently pure to be non-acid.

Films prepared from the hereinabove described compositions are flexible, smooth, transparent, strong, substantially colorless, substantially Waterproof, are unafi'ected by ordinary hotographic baths, and in addition, com ine unexpectedly low inflammability with high resistance against brittleness upon prolonged heating at 65 (1, or equivalent conditions in actual use. The amount of alkali in the film is, of course, insufiicient to impair their transparency.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

l, A composition of matter comprising substantially the following: 100 parts by weight of water insoluble ethyl cellulose; 20

parts of bromcamphor substantially free from uncombined bromine and hydrobromic acid, and more than 300 parts of a volatile common solvent, said composition comprising snfiicient inorganic alkali to give it an alkalinity in excess of Ph.,.

2. A fiowable composition comprising 100 parts by weight of water-insoluble ethyl cellulose, 5 to 50 parts of brom'camphor substantially free from uncombined bromine and 'hydrobromic acid, and more than 300 parts of a volatile common solvent, said composition comprising sufiicient inorganic alkali to give it an alkalinity in excess ofcomprising colloidized water-insoluble celv.

lulose ether and bromcamphor substantially free from uncombined bromine and hydrobromic acid, said film having distributed therein suflicient inorganic alkali to give the film an alkalinity in excess of P11 the proportions of the ingredients being such that the film is flexible, transparent and inert to photographic emulsions.

4. As an article of manufacture a film comprising colloidized Water-insoluble ethyl cellulose and bromcamphor free from uncombined bromine'and hydrobromic acid, said film having uniformly distributed therein suflicient inorganic alkali to give the film an alkalinity in excess of Pb the amount of alkali being insuflicient to impair the transparency of the film, the proportions of the ingredients being such that .the film is flexible, transparent and inert to photographic emulsions.

'Signed at Rochester, New York, this 29th day of July, 1926.

STEWART J. CARROLL. 

